On the third day it was my turn to test God's vigilance, letting the metal chair plop me down into the cool pond like a piece of bait. Treading water, I adjusted my eyes to the moonlight of the cave. The cenote was shaped like an old Chianti bottle—a narrow neck leading to a wide chamber about 90 feet (30 meters) across and 120 feet (40 meters) deep. The bottle was half full, the water surface 35 feet (11 meters) below the domed ceiling. Stalactites dripped, and the roots of trees were spread on the walls in delicate dark webbing. Spanish records tell how live victims were thrown into the sacred cenote at Chichén Itzá, a major Maya city, on the premise that, as sacrifices to the gods, they would not die—even though they were never seen again. I scanned the slick limestone walls, and my heart pounded, feeling their terror.

Sinking deeper into the white noise of pressure, I bottomed out at 50 feet (20 meters) and glided across piles of shattered limestone. A side cave, shaped like a sock, spun down and off to the west. Resting in the sand was a mahogany-hued skeleton, already tagged, the eye orbits of its skull bleak with expectations of eternity.

A few days later the National Instutute of Anthropology and History scientists brought him up. It was the first skeleton of its kind—with all its bones in their natural positions, undisturbed—ever found underwater in the Yucatán. He was a large man, perhaps 50 years old, well past the Maya life expectancy. "His health was bad," said Terrazas after examining the bones, "with arthritis so severe that he could barely flex his hands. He had terrible teeth problems—gingivitis—and he probably had a very hard time chewing."

He was lying face up on the sand. Was it an accident? "No," said Terrazas. "There are nine skeletons down there [eight are partial]. Maybe one is there from an accident, but not nine."

When the car winch pulled up the bones of the old man, the three women who had made quesadillas for us the previous night were standing by the well. I asked them what they thought of our mission. "We didn't expect skeletons," said one, Olegaria Chiku. "For us, a cenote is just a hole with water. But my mother lived around here, and she said that we needed to give the cenote 15 virgins, and God would open up a road to bring in the gold that we know is down there."

Until the 1960s many people, including many archaeologists, thought virgins were the only individuals whose stories had ended in the cenotes. "We learned then that they were not all young girls," said Carmen Rojas, the underwater archaeologist who oversees data processing for the survey project. "And now we know that they were not all sacrifices."

How can anthropologists perform their research on ancient human remains and, at the same time, respect the traditions of descendants who believe the dead should not be disturbed?

In More to Explore the National Geographic magazine team shares some of its best sources and other information. Special thanks to the Research Division.

There are more than six million Maya living in Guatemala, Mexico, Honduras, El Salvador, and Belize. Although many Maya were wiped out by the Spanish Conquest in the 16th century, either through conflict or introduced diseases, some survived, but were stripped of their wealth and power and were prevented from practicing their religion. Their ancient codices were burned, and Maya script was prohibited. Vast amounts of information about their deities, rituals, cosmology, and history were lost forever.

Yet the surviving Maya clung to their traditions, allowing many hallmarks of their culture to endure. In remote villages, where Spanish administrators' power was weak, families held on to their agricultural way of life, preserving the heart of Maya society. Today most Maya families farm and buy and sell goods in centralized markets as their ancestors once did. Some also practice the crafts of their ancestors, such as weaving, painting, and sculpting. Modern Maya religion has retained many ancient beliefs and rituals while incorporating elements of Catholicism. Ceremonies performed throughout the year honor the Maya's ancestors and the saints that have replaced the ancient gods. While in the highlands, communities still have "day-keepers," shamans who keep count of the 260-day calendar and perform elaborate rituals based on the time of year.

Some ethnologists wonder if Maya culture will continue to survive the pressures of the modern world. There are 31 Maya groups throughout Central America, all with their own dialect. Some, such as the Tzotil in Mexico, number more than 100,000, while others, such as the Lacandón of the Chiapas rain forest, consist of a few hundred people. The smaller groups are more fragile, but they all face threats from tourism, deforestation, economic devastation, and political upheaval.